Ultrasonic diagnostic scanning for three dimensional display

ABSTRACT

An ultrasonic diagnostic system and scanning technique are described for producing three dimensional ultrasonic image displays utilizing power Doppler signal information. In a preferred embodiment the power Doppler signal information is displayed in the absence of structural (B mode) information to reduce image clutter and provide three dimensional image segmentation. An ultrasonic scanning technique is presented for acquiring diagnostic three dimensional ultrasonic images of power Doppler intensity through manual hand scanning of a patient, without the need for specially fabricated scanning mechanisms or devices.

This invention relates to improvements in ultrasonic diagnostic imagingtechniques, and in particular to ultrasonic scanning of the body toacquire Doppler information for presentation in a three dimensionalimage format.

Various methods and devices have been proposed for ultrasonicallyscanning a volume within a subject for three dimensional analysis anddisplay. Many of these techniques involve the scanning of a number ofspatially adjacent image planes. The ultrasonic information from theseassociated planes can be analyzed and displayed on the basis of spatialcoordinates of the data within a plane, and on the basis of the spatialrelationship of each plane to the others. The information can bedisplayed in a three dimensional image format such as a perspective viewof the volume being imaged.

A number of scanning techniques utilizing specially devised scanningdevices have been proposed for acquiring these spatially related imageplanes. The article "Three-Dimensional Reconstruction of EchocardiogramsBased On Orthogonal Sections," by S. Tamura et al., Pattern Recognition,vol. 18, no. 2, pp 115-24 (1985) discusses three such devices: a guiderail to guide an ultrasonic probe while acquiring parallel image planes;a jointed arm in which sensors in the arm joints provide spatialcoordinates for the transducer; and rotation of a transducer about thecardiac long axis. A rotating transducer probe for the latter purpose isshown and described in "Multidimensional Ultrasonic Imaging forCardiology," by H. McCann et al., Proceedings of the IEEE, vol. 76, no.9, pp 1063-73 (Sept. 1988). It would be preferable, however, to be ableto acquire multiple image planes for three dimensional presentationwithout the need for special scanning devices or apparatus.

Ultrasonic images are subject to image artifacts arising from a numberof sources such as reverberation, multipath echoes, and coherent waveinterference. These artifacts will manifest themselves in various waysin the image which can be broadly described as image clutter. The imageclutter becomes particularly troublesome when images are presented in athree dimensional format, as the three dimensional clutter can interferewith and obscure pathology which the clinician is attempting todiagnose. Accordingly it would be desirable to provide ultrasonic imageinformation in a format in which clutter does not significantly impairthe pathology being viewed.

In accordance with the principles of the present invention the presentinventors have addressed this problem of obscuring clutter through theuse of ultrasonic Doppler information signals. Doppler information hasbeen used to image the body in two distinct ways. One Doppler imagingtechnique is commonly referred to as color Doppler velocity imaging. Asis well known, this technique involves the acquisition of Doppler dataat different locations called sample volumes over the image plane of anultrasonic image. The Doppler data is acquired over time and used toestimate the Doppler phase shift or frequency at each discrete samplevolume. The Doppler phase shift or frequency corresponds to the velocityof tissue motion or fluid flow in vessels within the body, with thepolarity of the shift indicating direction of motion or flow. Thisinformation is color coded in accordance with the magnitude of the shift(velocity) and its polarity, and overlaid over a structural image of thetissue in the image plane to define the structure of the moving organsor vessels in which fluids are flowing. The colors in the image therebyprovide an indication of the speed of blood flow and its direction inthe heart and blood vessels, for instance.

A second Doppler technique is known as color power Doppler. Thistechnique is unconcerned with estimations of the velocity of motion orfluid flow. Rather, it focuses simply on the intensity of the receivedsignals which exhibit a Doppler shift. This Doppler signal intensity canbe measured at each sample volume in an image plane and displayed in acolor variation. Unlike color Doppler velocity imaging, color powerDoppler does not present the problems of directionality determination,aliasing, and low sensitivity which are characteristic of velocityimaging. Color power Doppler simply displays the Doppler signalintensity at a sample volume in a coded color. Like color Dopplervelocity imaging, the color power Doppler display is overlaid with astructural B mode image to define the organ or tissue structure in whichmotion is occurring. Since the value at each sample volume can beaveraged over time or based upon a peak value, and is not subject to theconstant changes of velocity and direction which are characteristic ofthe pulsatility of Doppler velocity signals, the color power Dopplerdisplay can be presented as a more stable display of motion or flowconditions in the body.

In accordance with the principles of the present invention, a threedimensional ultrasonic display technique is provided which utilizespower Doppler signal information. The present inventors have utilizedpower Doppler images in an unconventional way, which is in the absenceof structural (B mode) information. The present inventors havediscovered that utilizing power Doppler information alone in a threedimensional display eliminates the substantial clutter contribution ofthe structural information signals, eliminates pulsatility variation,provides excellent sensitivity to low energy flow signals, reducesDoppler angle effects, and provides a segmentation of the flow or motioncharacteristics in the three dimensional image. The present inventorsalso present a technique for acquiring diagnostic three dimensionalultrasonic images through manual hand scanning of a patient, without theneed for specially fabricated scanning mechanisms or devices.

In the drawings:

FIG. 1 is a block diagram of an ultrasonic diagnostic imaging systemconstructed in accordance with the principles of the present invention;

FIG. 2 illustrates the manual scanning of a bifurcation in the body of apatient;

FIGS. 3a-3e illustrate a sequence of two dimensional Doppler powerimages acquired from the bifurcation of FIG. 2;

FIG. 4 illustrates the relation of the image planes of FIGS. 3a-3e tothe structure of the bifurcation of FIG. 2;

FIGS. 5a and 5b are a comparison of the bifurcation of FIG. 2 to a threedimensional Doppler power display of the blood flow of the bifurcation;

FIGS. 6a-6d illustrates the three dimensional relationship of manuallyacquired two dimensional image planes;

FIG. 7 illustrates a scanning aid for manually acquiring uniformlyspaced image planes; and

FIG. 8 is a flow chart used to explain the preferred technique forprocessing Doppler power images for three dimensional display.

Referring first to FIG. 1, a block diagram of an ultrasonic diagnosticimaging system constructed in accordance with the principles of thepresent invention is shown. An ultrasonic probe 10 includes amultielement transducer 12 which transmits waves of ultrasonic energyinto the body of a patient and receives ultrasonic echoes returning fromstructures in the body. In the case of ultrasonic wave transmission forDoppler interrogation of the body, it is the echoes returning frommoving tissue, blood and other fluids in the body that are of interest.The ultrasonic probe 10 is connected to a transmitter/receiver 14 whichalternately pulses individual elements of the transducer to shape andsteer an ultrasonic beam, and receives, amplifies and digitizes echosignals received by the transducer elements following each pulsetransmission.

The transmitter/receiver 14 is coupled to a beamformer 16 which controlsthe times of activation of specific elements of the transducer 12 by thetransmitter/receiver. This timing enables the transducer 12 to transmita shaped and focused ultrasound beam in a desired direction. Thebeamformer 16 also receives the digitized echo signals produced by thetransmitter/receiver during echo reception and appropriately delays andsums them to form coherent echo signals.

The echo signals produced by the beamformer 16 are coupled to a B modeprocessor 30 and an I,Q demodulator 18. The B mode processor processesthe amplitude information of the echo signals on a spatial basis for theformation of a structural image of the tissue in the area of the patientbeing scanned. The I,Q demodulator 18 demodulates the received echosignals into quadrature components for Doppler processing. The I,Qcomponents are filtered by a wall filter 20 to remove low frequencyartifacts stemming from the movement of vessel walls in applicationswhere it is only the motion of flowing fluids such as blood that is ofinterest. The filtered I,Q components are then applied to a Dopplershift estimation processor 22 and a Doppler power estimation processor24.

The Doppler shift estimation processor 22 operates in the conventionalmanner to estimate a Doppler phase or frequency shift from the I,Qcomponents at each sample volume location of the image field. TheDoppler shift estimation processor operates on a number of signalsamples resulting from the interrogation of each sample volume locationby an ensemble of Doppler interrogation pulses. The sample volume valuesare applied to a velocity image processor 26 which maps the values tocolor values for display. The color values are applied to a scanconverter and display processor 32 which spatially arranges the colorvalues in the desired image format. The color values are displayed aspixels on a display 40, wherein each color represents a particularvelocity of flow in a particular direction at that pixel location. Thecolor flow velocity information is overlaid with a structural image ofthe interior of the body utilizing the structural information providedby the B mode processor 30. This compound image shows both the directionand velocity of blood flow, as well as the structure of the vessels ororgans which contain the flowing blood.

In accordance with the principles of the present invention the Dopplersystem of FIG. 1 also includes a power Doppler imaging capability. Thepower Doppler components include a Doppler power estimation processor 24which estimates the Doppler signal power magnitude from the I,Q signalcomponents at each sample volume location using the expression (I²+Q²)^(1/2). The Doppler power estimates at each location can beprocessed and displayed in real time or can be averaged with earlieracquired power estimates for each sample volume location. In a preferredembodiment, each sample volume location is interrogated by a number ofpulses and the estimation processor 24 utilizes the signals obtainedfrom all interrogations in the estimations of Doppler power at thesample volume locations. These Doppler power estimates are mapped todisplay intensity or color values by a power image processor 28. Thedisplay values with their spatial coordinates are stored in separateplanar images in an image sequence memory 34 and are also applied to thescan converter and display processor 32 which spatially arranges theDoppler power display values in the desired image format, e.g., sectoror rectangular. The two dimensional Doppler power images may then bedisplayed on a display 40 or recalled from the image sequence memory 34for three dimensional processing using a peak detector 36 for maximumDoppler power intensity detection as discussed below. User operation ofthe system of FIG. 1 is effected through various user controls 42 whichenable the user to select the type of imaging to be performed, i.e., Bmode, color velocity Doppler or Doppler power imaging, and to store andretrieve images from the image sequence memory 34 for three dimensionaldisplay, for example.

FIG. 2 illustrates the use of the ultrasonic probe 10 to manuallyacquire a sequence of image planes for three dimensional display. Aportion of the probe cable 11 leading to the transmitter/receiver of theultrasound system is shown at the top of the probe. The transduceraperture of the probe 10 is in contact with the skin of the patient overthe region of the body which is to be scanned. The skin of the patientis represented by a layer 50 in the drawing. In this example the regionof the patient being scanned includes a blood vessel bifurcation 52having a small vessel 54 branching out from a larger vessel 56. Blood isflowing inside the structural walls of the vessels as indicated at 60and 62.

The bifurcation 52 may be scanned by rocking or fanning the probe 10while it is in contact with the patient. In a preferred technique theprobe aperture slides over the skin 50 as indicated by arrow 58 to scanthe bifurcation region with a plurality of substantially parallel imageplanes. One such image plane 64, here shown as a sector, is seenprojecting from the transducer aperture of the probe. The relation ofthe image plane 64 to the probe is denoted by an image plane marker 13on the side of the probe case. The marker 13 is in the same plane as theimage plane 64, and denotes the upper left side of the image in itsuninverted display orientation.

In accordance with the present invention, the ultrasound system acquiresand processes power Doppler information from a plurality of image planesas the probe slides over the bifurcation region of the patient asindicated by the arrow 58. The duration of such a scan can typicallylast about ten to twenty seconds, during which time 100 to 200 imageplanes of power Doppler information are acquired, processed and storedin the image sequence memory 34. This image information is processed todetect and record the maximum Doppler intensity at a number of differentviewing angles over a range of such viewing angles as discussed below.

FIGS. 3a-3e shows a five image plane sequence which illustrates theprinciples of the power Doppler three dimensional imaging technique ofthe present invention. The five image planes of the sequence arereferenced to the structure of the bifurcation 52 in FIG. 4, which is aview of the top of the two vessels. FIG. 3a is a power Doppler imagetaken along plane 3a of FIG. 4, which is seen to intersect the upperedge of the blood flow of the large vessel 56, just inside the vesselwall 56'. In FIG. 3b the image plane intersects a greater cross section72 of the blood flow of the large vessel 56, and the edge 74 of theblood flow of the small vessel 54, just inside the vessel wall 54' asplane 3b of FIG. 4 shows. The image plane of FIG. 3c intersects thecenters of both vessel as is seen by plane 3c in FIG. 4. In FIG. 3d theimage plane moves down to a lesser cross section of both vessels and theplane 3e of FIG. 3e intersects only the peripheral blood flow in thelarge vessel 56.

The images of FIGS. 3a-3e are processed and presented together in athree dimensional presentation as illustrated in FIG. 5b. The threedimensional image is seen to comprise the power Doppler informationwithout any structural image overlay. This is clearly seen by comparingthe three dimensional power Doppler image 80 of FIG. 5b with thesimilarly scaled rendering of the bifurcation 52 in FIG. 5a. Therendering of FIG. 5a is seen to include the structure of the vesselwalls 54' and 56' which contain flowing blood indicated at 60 and 62.The power Doppler image 80, resulting from the Doppler detected movementof the flowing blood, is displayed without any B mode structure of thevessel walls 54' and 56'. It has been found that omitting the vesselwalls from the three dimensional display does not diminish theeffectiveness of the display, as the continuity of the blood flowintensity serves to define the paths in which blood is flowing. Inaddition, the absence of B mode echos eliminates considerable structuralecho clutter from the image. The image is clearly segmented by the flowselectivity, and the smoothly varying stability and sensitivity of themaximum intensity power Doppler information.

FIG. 8 is a flowchart illustrating a preferred technique for processinga sequence of planar Doppler power images for real time threedimensional display. As described above, the Doppler power displayvalues with their spatial coordinates are stored in a sequence of planarimages in the image sequence memory 34, as shown by step 80 in FIG. 8.The images of FIGS. 3a-3e are illustrative of such a two dimensionalimage sequence. In step 82 the process receives processing parametersprovided by the user controls. One parameter is the range of viewingangles, θ₁ -θ_(M), over which the three dimensional presentation is tobe viewed. The other parameter is the increment Δθ between each viewingangle in the range. For instance the user could input a range of viewingangles of +60° to -60°, referenced to a line of view in a plane which isnormal to the plane of the first image in the sequence, and a rangeincrement of 1°. From these inputs the number of three dimensionalprojections needed is computed in step 82. In this example 121projections are needed to display a 120° range span in one degreeincrements.

The process now begins to form the necessary sequence of 121 maximumintensity projections. In step 84 the planar Doppler power images arerecalled from the image sequence memory for sequential processing by thescan converter and display processor 32. In step 86 each planar image isrotated to one of the viewing angles θ_(n), then projected back to theviewing plane. In step 88 the pixels of the projected planar images areaccumulated on a maximum intensity basis. Each projected planar image isoverlaid over the previously accumulated projected images but in atransposed location in the image plane which is a function of theviewing angle and the interplane spacing: the greater the viewing angle,the greater the transposition displacement from one image to the next.The display pixels chosen from the accumulated images are the maximumintensity pixels taken at each point in the image planes from all of theoverlaid pixels accumulated at each point in the image. This effectivelypresents the maximum intensity of Doppler power seen by the viewer alongevery viewing line between the viewer and the three dimensional image.In a preferred embodiment the relocation of image points after rotationabout the y axis, projection and transposition may be expressed as:##EQU1## and the relocation of image points after rotation about the xaxis, projection and transposition may be expressed as: ##EQU2## where θis the angle of rotation, (x, y, z) are the coordinates of a point to berelocated, and (x', y') are the coordinates of a point in the viewingplane after relocation.

After all of the planar images have been rotated, projected, transposed,overlaid, and the maximum intensities at each pixel chosen, theresulting three dimensional image for the viewing angle θ_(n) is storedin the image sequence memory 34 as a brightness modulated monochromeimage in a three dimensional image sequence. In step 92 the processreturns to step 84 and proceeds through steps 84-92 until the full threedimensional image sequence has been stored in memory. In the presentexample this is a sequence of 121 three dimensional images over therange of +60° to -60°.

The stored three dimensional sequence is now available for recall anddisplay in step 94 upon command of the user. As the sequence is recalledand displayed in real time, the user sees a three dimensionalpresentation of the motion or fluid flow occurring in the volumetricregion over which the planar images were acquired. The volumetric regionis viewed three dimensionally as if the user were moving around theregion and viewing the motion or flow from changing viewing angles. Inthis particular example the user has the impression of moving over arange of viewing angles spanning 120° around the volumetric region. Theviewer can sweep back and forth through the sequence, giving theimpression of moving around the volumetric region in two directions.

FIGS. 6a-6d illustrate the effects of nonuniform spacing of image planeswhich can arise from manual image plane scanning. FIG. 6a is a top viewof the large vessel 56, showing the blood flow 60 surrounded by thevessel wall 56' for reference. FIG. 6b shows another sequence of fiveimage planes taken across the vessel but unlike the sequence of FIG. 4,these image planes are unevenly spaced. Image planes 1 and 2 are seen tobe more widely spaced than the closer spacing of image planes 4 and 5.Such a spacing will result for instance when the probe slides fasterwhen acquiring image planes 1 and 2 and slows down as it approaches thepositions of image planes 4 and 5. This sequence is acquired by manuallysliding the probe from left to right at a progressively slower speedacross the skin above the vessel 56.

In a constructed embodiment of the present invention the image planesare assumed to be evenly spaced across the imaged volume and areprocessed and displayed accordingly. FIG. 6c shows the five image planesof FIG. 6b from above when they are evenly spaced for display. Theresult of this spacing is more readily seen in FIG. 6d, in which theborder of the blood flow and the vessel wall 56" have been reconnectedfor ease of illustration. The arrows at 78 illustrate the uniform imageplane spacing, which is slightly less than the spacing of image planes 1and 2 in FIG. 6b and slightly greater than the spacing of image planes 5and 6 in that drawing. The effect is to give the cross sectional area ofthe blood flow a slightly oblong appearance in which the left side ofthe flow area is compressed and the right side extended in relation tothe actual proportions of the blood flow area.

The present inventors have observed that this distortion of the aspectratio of the three dimensional image does not noticeably detract fromthe effect of the overall three dimensional display. Even with suchaspect distortion the three dimensional image continues to show therelative paths and orientations of blood vessels and the continuity orstenosis of flow in vessels in a manner not achieved by two dimensionalpresentations. The continuity of flow paths and display effectiveness isenhanced by displaying the Doppler power on the basis of the maximumsignal intensity. When the image planes are acquired from a range ofacquisition angles the use of the maximum intensity display has theeffect of diminishing sensitivity variation resulting from Doppler angleeffects. The image planes may be concurrently displayed in the form of asurface rendering or a transparency of the blood flow information, but apreferred presentation is a monochrome display of the varying brightnessof the maximum intensity pixels of the combined images of a volumetricregion as described above. The flow and perfusion of the blood supply inan organ such as a kidney is more completely displayed with a threedimensional power Doppler image than can be accomplished with a twodimensional presentation. The technique is well suited for assessing thesuccess of organ transplants, for instance.

Simple aids may be provided to improve the accuracy of manual threedimensional scanning if desired. One such aid is shown in FIG. 7, andcomprises a ruler scale printed on a clear strip of surgical tape. Thetape is applied to the skin of the patient adjacent to the probe, andthe probe is moved along the scale with the marker 13 on the probe usedas a reference. Image planes can be acquired at each marker on thescale, or the scale can be traversed in a given time such as twentyseconds. Other aids may also be supplied by the ultrasound system suchas audible signals or lights telling the user when to start and stopmovement of the probe, and when the moving probe should be passing eachmarker on the scale.

The imaging techniques of the present invention including particularlythat of FIG. 8 can be applied to a sequence of planar images acquiredwith position sensing of the image planes for display of anatomicallyprecise images. An advantageous Doppler technique for sensing thepositions of the image planes and lines in each plane in relation toeach other is described in U.S. Pat. No. 5,127,409. When the positionsof the image planes or lines are known in relation to each other thethree dimensional processor no longer has to assume uniform spacingbetween two dimensional planes, but can utilize the measured spacingbetween three dimensional display elements to form more geometricallyaccurate three dimensional images.

What is claimed is:
 1. A method for producing three dimensionalultrasonic images of the interior of a body comprising the stepsof:transmitting ultrasonic waves over a volumetric region of theinterior of the body; receiving ultrasonic Doppler information signalsfrom spatial locations within said region; processing said ultrasonicDoppler information signals to determine the Doppler power intensityreceived from said locations within said region; and displaying saidDoppler power intensity on a spatial basis in a three dimensionalpresentation.
 2. The method of claim 1, wherein said step of processingcomprises the step of processing said ultrasonic Doppler informationsignals to determine the maximum Doppler power intensity received fromsaid locations within said region; andwherein said step of displayingcomprises the step of displaying said maximum Doppler power intensity ofsaid locations on a spatial basis in a three dimensional presentation.3. The method of claim 2, wherein said step of transmitting comprisesthe step of transmitting ultrasonic waves over a series of planarregions of a volumetric region of the interior of the body; andwhereinsaid step of receiving comprises the step of receiving ultrasonicDoppler information signals from spatial locations within said planarregions.
 4. The method of claim 3, wherein said step of processingcomprises the step of processing said ultrasonic Doppler informationsignals in spatially related image planes to determine the Doppler powerintensity received from said locations within each of said image planes;andwherein the step of displaying comprises the step of concurrentlydisplaying said Doppler power intensity of a plurality of said imageplanes on a spatial basis in a three dimensional presentation.
 5. Themethod of claim 4, further comprising the step of identifying themaximum Doppler power intensity at each point in a combination of saidspatially related image planes; andwherein the step of displayingcomprises the step of displaying said identified maximum Doppler powerintensities on a spatial basis in a three dimensional display.
 6. Themethod of claim 1, wherein said step of displaying comprises the step ofdisplaying said Doppler power intensity on a spatial basis in theabsence of structural echo information signals in a three dimensionalpresentation.
 7. .[.The method of claim 1,.]. .Iadd.A method forproducing three dimensional ultrasonic images of the interior of a bodycomprising the steps of:transmitting ultrasonic waves over a volumetricregion of the interior of the body; receiving ultrasonic Dopplerinformation signals from spatial locations within said region;processing said ultrasonic Doppler information signals to determine theDoppler power intensity received from said locations within said region;and displaying said Doppler power intensity on a spatial basis in athree dimensional presentation, .Iaddend. further comprising the step ofproviding said transmitting and receiving steps by manually moving anultrasonic transducer probe which is in contact with said body.
 8. Anultrasonic diagnostic imaging system which is capable of providing threedimensional presentations of the interior of a body comprising:anultrasonic transducer probe for transmitting ultrasonic waves over avolumetric region of the interior of the body and for receivingultrasonic Doppler information signals returned from spatial locationswithin said region; a power Doppler processor responsive to saidultrasonic Doppler information signals for producing Doppler powerintensity signals corresponding to said locations within said region; animage processor for processing said Doppler power intensity signals fordisplay in a three dimensional image presentation; and a display coupledto said image processor which displays said three dimensional imagepresentation.
 9. The ultrasonic diagnostic imaging system of claim 8,wherein said image processor comprises means responsive to said Dopplerpower intensity signals for producing a maximum Doppler power intensityimage of said region.
 10. The ultrasonic diagnostic imaging system ofclaim 9, wherein said ultrasonic transducer probe comprises means fortransmitting ultrasonic waves over a series of image planes of avolumetric region of the interior of the body and for receivingultrasonic Doppler information signals returned from spatial locationswithin said image planes of said region.
 11. The ultrasonic diagnosticimaging system of claim 10, wherein said image processor furthercomprises means for processing said Doppler power intensity signals inspatially related image planes to determine the Doppler power intensitycorresponding to locations within each of said image planes; andwhereinsaid display further comprises means for concurrently displaying saidDoppler power intensity of a plurality of said image planes on a spatialbasis in a three dimensional presentation.
 12. The ultrasonic diagnosticimaging system of claim 11, further comprising a peak detectorresponsive to the Doppler power intensity determinations correspondingto locations within each of said image planes for identifying themaximum Doppler power intensity at points in a combination of aplurality of image planes; andwherein said display comprises means fordisplaying maximum Doppler power intensity images in the absence ofconcurrent display of tissue structure.
 13. The ultrasonic diagnosticimaging system of claim 8, wherein said image processor furthercomprises means for processing said Doppler power intensity signals fordisplay in the absence of tissue structure information signals in athree dimensional image presentation.
 14. The ultrasonic diagnosticimaging system of claim 13, further comprising a peak detectorresponsive to said Doppler power intensity signals for identifying themaximum Doppler power intensity corresponding to said locations withinsaid image planes.
 15. The ultrasonic diagnostic imaging system of claim14, wherein said ultrasonic transducer probe comprises a manual scannerwhich is manually moved in relation to said volumetric region to scan asequence of spatially related image planes in said region.
 16. Anultrasonic diagnostic imaging system which is capable of providing threedimensional presentations of a region of a body comprising:an ultrasonictransducer probe for transmitting ultrasonic waves over a sequence ofimage planes of said region of the body and for receiving ultrasonicDoppler information signals returned from spatial locations within saidimage planes while said probe is manually incremented positionally inrelation to said region; a power Doppler processor responsive to saidultrasonic Doppler information signals for estimating the Doppler powercorresponding to said locations within said image planes; an imageprocessor for processing said Doppler power estimates to produce amaximum Doppler power image for display in a three dimensional imagepresentation in the absence of non Doppler signal information; and adisplay responsive to the production of maximum Doppler power imageswhich displays a sequence of said maximum Doppler power images in athree dimensional image presentation in the absence of a structuraldisplay of tissue.
 17. The ultrasonic diagnostic imaging system of claim16, wherein said image processor comprises means for accumulating saidestimates of Doppler power of a plurality of said image planes to form athree dimensional display image of the maximum Doppler power intensityas seen by a viewer from a given viewing perspective.
 18. The ultrasonicdiagnostic imaging system of claim 17, further comprising an imagesequence memory for storing said estimates of Doppler power incorresponding images and for storing a sequence maximum Doppler powerimages. .Iadd.
 19. A method for producing three dimensional ultrasonicimages of the interior of a body comprising the steps of:transmittingultrasonic waves over a volumetric region of the interior of the body;receiving ultrasonic information signals due to motion or flow fromspatial locations within said region; processing said ultrasonicinformation signals to determine locations within said region wheremotion or flow is present; and displaying said motion or flow on aspatial basis in a three dimensional presentation which does notdistinguish the direction of said motion or flow. .Iaddend..Iadd.20. Themethod of claim 19, wherein said ultrasonic information signals compriseDoppler information signals. .Iaddend..Iadd.21. The method of claim 19or 20, wherein said motion or flow is the motion or flow of blood, andwherein said spatial locations comprise the interior of blood vessels..Iaddend..Iadd.22. A method for producing three dimensional ultrasonicimages of the interior of a body comprising the steps of: transmittingultrasonic waves over a volumetric region of the interior of the body;receiving ultrasonic Doppler information signals from spatial locationswithin said region; processing said ultrasonic Doppler informationsignals to determine magnitude signals of motion or flow within saidregion; and displaying, in response to said magnitude signals, locationsof motion or flow within said region without regard to motion or flowdirectionality on a spatial basis in a three dimensional presentation..Iaddend..Iadd.23. The method of claim 22, wherein said displaying stepdisplays said magnitude signals without directional polarity on aspatial basis in a three dimensional presentation. .Iaddend..Iadd.24.The method of claim 22 or 23, wherein said ultrasonic Dopplerinformation signals result from the flow of blood within the body, andwherein said three dimensional presentation is ambiguous as to thedirection of said flow of blood. .Iaddend..Iadd.25. A method forproducing three dimensional ultrasonic images of the interior of a bodycomprising the steps of:transmitting ultrasonic waves over a volumetricregion of the interior of the body; receiving ultrasonic Dopplerinformation signals due to changing directional motion or flow fromspatial locations within said region; processing said ultrasonic Dopplerinformation signals to determine magnitude signals relating to spatiallocations within said region where motion or flow is present; anddisplaying the locations of said motion or flow on a spatial basis in athree dimensional presentation without regard to the direction of motionor flow. .Iaddend..Iadd.26. The method of claim 25, wherein thedirection of said motion or flow may be represented by the sign orpolarity of a Doppler signal, wherein said three dimensionalpresentation is ambiguous as to said sign or polarity..Iaddend..Iadd.27. The method of claim 25, wherein magnitude signalscorresponding to different directions of motion or flow are displayed ona common basis. .Iaddend..Iadd.28. An ultrasonic diagnostic imagingsystem which is capable of providing three dimensional presentations ofthe interior of a body comprising:an ultrasonic transducer probe fortransmitting ultrasonic waves over a volumetric region of the interiorof the body and for receiving ultrasonic information signals returnedfrom spatial locations within said region as the probe is free handscanned over said region; an image processor for processing saidultrasonic information signals for display in a three dimensional imagepresentation; and a display coupled to said image processor whichdisplays said three dimensional image presentation. .Iaddend..Iadd.29.An ultrasonic diagnostic imaging system which is capable of providingthree dimensional presentations of the interior of a body comprising: anultrasonic transducer probe for free hand image plane scanning of avolumetric region of the interior of the body and for receivingultrasonic information signals returned from spatial locations withinsaid region during said free hand image plane scanning; an imageprocessor for processing said ultrasonic information signals for displayin a three dimensional image presentation; and a display coupled to saidimage processor which displays said three dimensional imagepresentation. .Iaddend..Iadd.30. The ultrasonic diagnostic imagingsystem of claim 29, wherein said image processor processes saidultrasonic information signals without quantification of interplanespacing. .Iaddend..Iadd.31. The ultrasonic diagnostic imaging system ofclaim 30, wherein said image processor is operated on the basis ofuniform interplane spacing. .Iaddend..Iadd.32. The ultrasonic diagnosticimaging system of claim 29, wherein said probe provides said ultrasonicinformation signals to said image processor without position sensing ofimage planes. .Iaddend..Iadd.33. An ultrasonic diagnostic imaging systemwhich is capable of providing three dimensional presentations of theinterior of a body comprising: an ultrasonic transducer probe which isfree hand scanned to sweep transmitted ultrasonic waves over avolumetric region of the interior of the body and for receivingultrasonic information signals returned from spatial locations withinsaid region; an image processor for processing said ultrasonicinformation signals for display in a three dimensional imagepresentation; and a display coupled to said image processor whichdisplays said three dimensional image presentation. .Iaddend..Iadd.34.The ultrasonic diagnostic imaging system of claim 28, 29, or 33, whereinsaid image processor further comprises a Doppler processor; and whereinsaid display displays the location of motion or flow in said region in athree dimensional image presentation. .Iaddend..Iadd.35. A method forproducing three dimensional ultrasonic images of the interior of a bodycomprising the steps of: transmitting ultrasonic waves over a volumetricregion of the interior of the body; receiving ultrasonic informationsignals due to motion or flow from spatial locations within said region;processing said ultrasonic information signals to determine locationswithin said region where motion or flow is present, which does notdistinguish the direction of motion or flow; and displaying said motionor flow on a spatial basis in a three dimensional presentation in theabsence of adjacent B mode structure. .Iaddend..Iadd.36. The method ofclaim 35, wherein said processing step comprises Doppler processing saidultrasonic information signals to determine locations within said regionwhere motion or flow is present. .Iaddend..Iadd.37. An ultrasonicdiagnostic imaging system which is capable of providing threedimensional presentations of the interior of a body comprising: anultrasonic transducer probe for transmitting ultrasonic waves over avolumetric region of the interior of the body and for receivingultrasonic information signals returned from motion or flow at spatiallocations within said region; a signal processor for processing saidultrasonic information signals to determine locations within said regionwhere motion or flow is present; and a display coupled to signalprocessor for displaying said locations where motion or flow is presenton a spatial basis in a three dimensional image presentation which doesnot distinguish the direction of said motion or flow. .Iaddend..Iadd.38.The ultrasonic diagnostic imaging system of claim 37, wherein saidsignal processor comprises a Doppler signal processor..Iaddend..Iadd.39. The ultrasonic diagnostic imaging system of claim 38,wherein said motion or flow is bloodflow. .Iaddend..Iadd.40. Anultrasonic diagnostic imaging system which is capable of providing threedimensional presentations of the interior of a body comprising:anultrasonic transducer probe for transmitting ultrasonic waves over avolumetric region of the interior of the body and for receiving Dopplerinformation signals returned from motion or flow at spatial locationswithin said region; a signal processor for Doppler processing saidDoppler information signals to develop magnitude signals relating tolocations within said region where motion or flow is present; and adisplay responsive to said magnitude signals for displaying saidlocations where motion or flow is present on a spatial basis withoutregard to motion or flow directionality in a three dimensional imagepresentation. .Iaddend..Iadd.41. The ultrasonic diagnostic imagingsystem of claim 40, wherein said Doppler information signals arereturned from flowing blood, and wherein said three dimensional imagepresentation is ambiguous as to the direction of said bloodflow..Iaddend..Iadd.42. A method for producing three dimensional ultrasonicimages of the interior of a body by free hand scanning with anultrasound probe, comprising the steps of: transmitting ultrasonic wavesover a volumetric region of the interior of the body and receivingultrasonic information signals from spatial locations within said regionwhile free hand scanning said region with an ultrasound probe;processing said ultrasonic information signals for display in a threedimensional image presentation; and displaying a three dimensionalpresentation of said ultrasonic information signals. .Iaddend..Iadd.43.The method of claim 42, wherein said ultrasonic information signalscomprise Doppler information signals; and wherein said processing stepcomprises Doppler processing said information signals..Iaddend..Iadd.44. The method of claim 43, wherein said displaying stepcomprises displaying locations in said region where motion or flow ispresent in a three dimensional image presentation. .Iaddend..Iadd.45. Amethod for producing three dimensional ultrasonic images of the interiorof a body by free hand scanning with an ultrasound probe, comprising thesteps of:transmitting ultrasonic waves over a volumetric region of theinterior of the body and receiving ultrasonic information signals fromspatial locations within said region during free hand image planescanning with an ultrasound probe; processing said ultrasonicinformation signals for display in a three dimensional imagepresentation; and displaying a three dimensional presentation of saidultrasonic information signals. .Iaddend..Iadd.46. The method of claim45, wherein said processing step comprises processing ultrasonic planarimage signals for display in a three dimensional image presentationwithout quantification of interplane spacing. .Iaddend..Iadd.47. Themethod of claim 45, wherein said processing step comprises processingultrasonic planar image signals for display in a three dimensional imagepresentation on the basis of assumed uniform interplane spacing..Iaddend..Iadd.48. The method of claim 45, wherein said manual imageplane scanning is performed without position sensing of image planes..Iaddend..Iadd.49. An ultrasonic diagnostic imaging system which iscapable of providing three dimensional presentations of the interior ofa body comprising: an ultrasound probe which transmits ultrasonic wavesover a volumetric region of the interior of the body and receivesultrasonic information signals due to motion or flow from spatiallocations within said region; a processor coupled to receive saidultrasonic information signals which determines locations within saidregion where motion or flow is present which does not distinguish thedirection of motion or flow; and a display for displaying locationswhere said motion or flow is present on a spatial basis in a threedimensional presentation in the absence of adjacent B mode structure..Iaddend..Iadd.50. The ultrasonic diagnostic imaging system of claim 49,wherein said processor comprises a Doppler processor. .Iaddend.